The amyloid diseases (amyloidoses) are classified according to the type of amyloid protein present as well as the underlying disease. Amyloid diseases have a number of common characteristics including each amyloid consisting of a unique type of amyloid protein. The amyloid diseases include, but are not limited to, the amyloid associated with Alzheimer's disease, Down's syndrome, hereditary cerebral hemorrhage with amyloidosis of the Dutch type, dementia pugilistica, inclusion body myositosis (Askanas et al, Ann. Neurol. 43:521-560, 1993) and mild cognitive impairment (where the specific amyloid is referred to as beta-amyloid protein or Aβ), the amyloid associated with chronic inflammation, various forms of malignancy and Familial Mediterranean Fever (where the specific amyloid is referred to as AA amyloid or inflammation-associated amyloidosis), the amyloid associated with multiple myeloma and other B-cell dyscrasias (where the specific amyloid is referred to as AL amyloid), the amyloid associated with type 2 diabetes (where the specific amyloid protein is referred to as amylin or islet amyloid polypeptide or IAPP), the amyloid associated with the prion diseases including Creutzfeldt-Jakob disease, Gerstmann-Straussler syndrome, kuru and animal scrapie (where the specific amyloid is referred to as PrP amyloid), the amyloid associated with long-term hemodialysis and carpal tunnel syndrome (where the specific amyloid is referred to as M2-microglobulin amyloid), the amyloid associated with senile cardiac amyloidosis and Familial Amyloidotic Polyneuropathy (where the specific amyloid is referred to as transthyretin or prealbumin), and the amyloid associated with endocrine tumors such as medullary carcinoma of the thyroid (where the specific amyloid is referred to as variants of procalcitonin). In addition, the α-synuclein protein which forms amyloid-like fibrils, and is Congo red and Thioflavin S positive (specific stains used to detect amyloid fibrillar deposits), is found as part of Lewy bodies in the brains of patients with Parkinson's disease, Lewy body disease (Lewy in Handbuch der Neurologie, M. Lewandowski, ed., Springer, Berlin pp. 920-933, 1912; Pollanen et al, J. Neuropath. Exp. Neurol. 52:183-191, 1993; Spillantini et al, Proc. Natl. Acad. Sci. USA 95:6469-6473, 1998; Arai et al, Neurosci. Lett. 259:83-86, 1999), multiple system atrophy (Wakabayashi et al, Acta Neuropath. 96:445-452, 1998), dementia with Lewy bodies, and the Lewy body variant of Alzheimer's disease. For purposes of this disclosure, Parkinson's disease, due to the fact that fibrils develop in the brains of patients with this disease (which are Congo red and Thioflavin S positive, and which contain predominant beta-pleated sheet secondary structure), is now regarded as a disease that also displays the characteristics of an amyloid-like disease.
Systemic amyloidoses which include the amyloid associated with chronic inflammation, various forms of malignancy and familial Mediterranean fever (i.e. AA amyloid or inflammation-associated amyloidosis) (Benson and Cohen, Arth. Rheum. 22:36-42, 1979; Kamei et al, Acta Path. Jpn. 32:123-133, 1982; McAdam et al., Lancet 2:572-573, 1975; Metaxas, Kidney Int. 20:676-685, 1981), and the amyloid associated with multiple myeloma and other B-cell dyscrasias (i.e. AL amyloid) (Harada et al., J. Histochem. Cytochem. 19:1-15, 1971), as examples, are known to involve amyloid deposition in a variety of different organs and tissues generally lying outside the central nervous system. Amyloid deposition in these diseases may occur, for example, in liver, heart, spleen, gastrointestinal tract, kidney, skin, and/or lungs (Johnson et al, N. Engl. J. Med. 321:513-518, 1989). For most of these amyloidoses, there is no apparent cure or effective treatment and the consequences of amyloid deposition can be detrimental to the patient. For example, amyloid deposition in the kidney may lead to renal failure, whereas amyloid deposition in the heart may lead to heart failure. For these patients, amyloid accumulation in systemic organs leads to eventual death generally within 3-5 years. Other amyloidoses may affect a single organ or tissue such as observed with the Aβ amyloid deposits found in the brains of patients with Alzheimer's disease and Down's syndrome: the PrP amyloid deposits found in the brains of patients with Creutzfeldt-Jakob disease, Gerstmann-Straussler syndrome, and kuru; the islet amyloid (IAPP) deposits found in the islets of Langerhans in the pancreas of 90% of patients with type 2 diabetes (Johnson et al, N. Engl. J. Med. 321:513-518, 1989; Lab. Invest. 66:522 535, 1992); the α2-microglobulin amyloid deposits in the medial nerve leading to carpal tunnel syndrome as observed in patients undergoing long-term hemodialysis (Geyjo et al, Biochem. Biophys. Res. Comm. 129:701-706, 1985; Kidney Int. 30:385-390, 1986); the prealbumin/transthyretin amyloid observed in the hearts of patients with senile cardiac amyloid; and the prealbumin/transthyretin amyloid observed in peripheral nerves of patients who have familial amyloidotic polyneuropathy (Skinner and Cohen, Biochem. Biophys. Res. Comm. 99:1326-1332, 1981; Saraiva et al, J. Lab. Clin. Med. 102:590-603, 1983; J. Clin. Invest. 74:104-119, 1984; Tawara et al, J. Lab. Clin. Med. 98:811-822, 1989).
Alzheimer's disease is characterized by the accumulation of a 39-43 amino acid peptide termed the β-amyloid protein or Aβ, in a fibrillar form, existing as extracellular amyloid plaques and as amyloid within the walls of cerebral blood vessels. Fibrillar Aβ amyloid deposition in Alzheimer's disease is believed to be detrimental to the patient and eventually leads to toxicity and neuronal cell death, characteristic hallmarks of Alzheimer's disease. Accumulating evidence implicates amyloid, and more specifically, the formation, deposition, accumulation and/or persistence of Aβ fibrils, as a major causative factor of Alzheimer's disease pathogenesis. In addition, besides Alzheimer's disease, a number of other amyloid diseases involve formation, deposition, accumulation and persistence of Aβ fibrils, including Down's syndrome, disorders involving congophilic angiopathy, such as but not limited to, hereditary cerebral hemorrhage of the Dutch type, inclusion body myositosis, dementia pugilistica, cerebral β-amyloid angiopathy, dementia associated with progressive supranuclear palsy, dementia associated with cortical basal degeneration and mild cognitive impairment.
Alzheimer's disease also puts a heavy economic burden on society. A recent study estimated that the cost of caring for one Alzheimer's disease patient with severe cognitive impairments at home or in a nursing home, is more than $47,000 per year (A Guide to Understanding Alzheimer's Disease and Related Disorders). For a disease that can span from 2 to 20 years, the overall cost of Alzheimer's disease to families and to society is staggering. The annual economic toll of Alzheimer's disease in the United States in terms of health care expenses and lost wages of both patients and their caregivers is estimated at $80 to $100 billion (2003 Progress Report on Alzheimer's Disease).
Tacrine hydrochloride (“Cognex”), the first FDA approved drug for Alzheimer's disease, is a acetylcholinesterase inhibitor (Cutler and Sramek, N. Engl. J. Med. 328:808 810, 1993). However, this drug has showed limited success in producing cognitive improvement in Alzheimer's disease patients and initially had major side effects such as liver toxicity. The second FDA approved drug, donepezil (“Aricept”), which is also an acetylcholinesterase inhibitor, is more effective than tacrine, by demonstrating slight cognitive improvement in Alzheimer's disease patients (Barner and Gray, Ann. Pharmacotherapy 32:70-77, 1998; Rogers and Friedhoff, Eur. Neuropsych. 8:67-75, 1998), but is not believed to be a cure. Therefore, it is clear that there is a need for more effective treatments for Alzheimer's disease patients.
Parkinson's disease is another human disorder characterized by the formation, deposition, accumulation and/or persistence of abnormal fibrillar protein deposits that demonstrate many of the characteristics of amyloid. In Parkinson's disease, an accumulation of cytoplasmic Lewy bodies consisting of filaments of α-synuclein/NAC (non-Aβ component) are believed important in the pathogenesis and as therapeutic targets. New agents or compounds able to inhibit α-synuclein and/or NAC formation, deposition, accumulation and/or persistence, or disrupt pre-formed α-synuclein/NAC fibrils (or portions thereof) are regarded as potential therapeutics for the treatment of Parkinson's and related synucleinopathies. NAC is a 35 amino acid fragment of α-synuclein that has the ability to form amyloid-like fibrils either in vitro or as observed in the brains of patients with Parkinson's disease. The NAC fragment of α-synuclein is a relative important therapeutic target as this portion of α-synuclein is believed crucial for formation of Lewy bodies as observed in all patients with Parkinson's disease, synucleinopathies and related disorders.
A variety of other human diseases also demonstrate amyloid deposition and usually involve systemic organs (i.e. organs or tissues lying outside the central nervous system), with the amyloid accumulation leading to organ dysfunction or failure. These amyloid diseases (discussed below) leading to marked amyloid accumulation in a number of different organs and tissues, are known as systemic amyloidoses. In other amyloid diseases, single organs may be affected such as the pancreas in 90% of patients with type 2 diabetes. In this type of amyloid disease, the beta-cells in the islets of Langerhans in pancreas are believed to be destroyed by the accumulation of fibrillar amyloid deposits consisting primarily of a protein known as islet amyloid polypeptide (IAPP). Inhibiting or reducing such IAPP amyloid fibril formation, deposition, accumulation and persistence is believed to lead to new effective treatments for type 2 diabetes. In Alzheimer's disease, Parkinson's and “systemic” amyloid diseases, there is currently no cure or effective treatment, and the patient usually dies within 3 to 10 years from disease onset.
Systemic AA amyloidosis is characterized by the deposition and accumulation of insoluble fibrillar amyloid deposits consisting of the AA amyloid protein in a number of different organs including heart, kidney, liver, spleen, gastrointestinal tract, lungs, and skin. Such amyloid accumulation and persistence can be fatal especially if deposition includes the heart (leading to heart failure) or kidneys (leading to kidney failure). Systemic AA amyloidosis is generally associated with chronic inflammatory disorders and is observed in patients with rheumatoid arthritis, ankylosing spondylitis, inflammatory bowel disease, osteomyelitis, leprosy, tuberculosis, Hodgkin's disease, renal cell carcinoma, and a familial form of disease known as Familial Mediterranean Fever. Currently, there is no cure or effective treatment for systemic AA amyloidosis and the patient usually dies within 3-7 years from disease onset. It is estimated that in the US there are approximately 100,000 cases of systemic AA amyloidosis, whereas in Europe the number of cases are estimated to be 2-5 fold higher.
Currently there is only one major drug currently in clinical trials which has demonstrated only limited success with no evidence for any elimination of AA amyloid deposits in patients (www.drugs.com/nda/kiacta—061016.html, www.neurochem.com/PR184.htn). There is still an urgent need for the development of an effective treatment targeting AA amyloid deposits for patients who have acquired systemic AA amyloidosis.
Amyloid as a Therapeutic Target for Alzheimer's Disease
Alzheimer's disease is characterized by the deposition and accumulation of a 39-43 amino acid peptide termed the beta-amyloid protein, Aβ or β/A4 (Glenner and Wong, Biochem. Biophys. Res. Comm. 120:885-890, 1984; Masters et al., Proc. Natl. Acad. Sci. USA 82:4245-4249, 1985; Husby et al., Bull. WHO 71:105-108, 1993). Aβ is derived by protease cleavage from larger precursor proteins termed β-amyloid precursor proteins (APPs) of which there are several alternatively spliced variants. The most abundant forms of the APPs include proteins consisting of 695, 751 and 770 amino acids (Tanzi et al., Nature 31:528-530, 1988).
The small Aβ peptide is a major component that makes up the amyloid deposits of “plaques” in the brains of patients with Alzheimer's disease. In addition, Alzheimer's disease is characterized by the presence of numerous neurofibrillary “tangles”, consisting of paired helical filaments which abnormally accumulate in the neuronal cytoplasm (Grundke-Iqbal et al., Proc. Natl. Acad. Sci. USA 83:4913-4917, 1986; Kosik et al., Proc. Natl. Acad. Sci. USA 83:4044-4048, 1986; Lee et al., Science 251:675-678, 1991). The pathological hallmark of Alzheimer's disease is therefore the presence of “plaques” and “tangles”, with amyloid being deposited in the central core of the plaques. The other major type of lesion found in the Alzheimer's disease brain is the accumulation of amyloid in the walls of blood vessels, both within the brain parenchyma and in the walls of meningeal vessels that lie outside the brain. The amyloid deposits localized to the walls of blood vessels are referred to as cerebrovascular amyloid or congophilic angiopathy (Mandybur, J. Neuropath. Exp. Neurol. 45:79-90, 1986; Pardridge et al., J. Neurochem. 49:1394-1401, 1987)
For many years there has been an ongoing scientific debate as to the importance of “amyloid” in Alzheimer's disease, and whether the “plaques” and “tangles” characteristic of this disease were a cause or merely a consequence of the disease. Within the last few years, studies now indicate that amyloid is indeed a causative factor for Alzheimer's disease and should not be regarded as merely an innocent bystander. The Alzheimer's Aβ protein in cell culture has been shown to cause degeneration of nerve cells within short periods of time (Pike et al., Br. Res. 563:311-314, 1991; J. Neurochem. 64:253-265, 1995). Studies suggest that it is the fibrillar structure (consisting of a predominant β-pleated sheet secondary structure), characteristic of all amyloids, that is responsible for the neurotoxic effects. Aβ has also been found to be neurotoxic in slice cultures of hippocampus (Harrigan et al., Neurobiol. Aging 16:779-789, 1995) and induces nerve cell death in transgenic mice (Games et al., Nature 373:523-527, 1995; Hsiao et al., Science 274:99-102, 1996). Injection of the Alzheimer's Aβ into rat brain also causes memory impairment and neuronal dysfunction (Flood et al., Proc. Natl. Acad. Sci. USA 88:3363-3366, 1991; Br. Res. 663:271-276, 1994).
Probably, the most convincing evidence that Aβ amyloid is directly involved in the pathogenesis of Alzheimer's disease comes from genetic studies. It was discovered that the production of Aβ can result from mutations in the gene encoding, its precursor, β-amyloid precursor protein (Van Broeckhoven et al., Science 248:1120-1122, 1990; Murrell et al., Science 254:97-99, 1991; Haass et al., Nature Med. 1:1291-1296, 1995). The identification of mutations in the beta-amyloid precursor protein gene that cause early onset familial Alzheimer's disease is the strongest argument that amyloid is central to the pathogenetic process underlying this disease. Four reported disease-causing mutations have been discovered which demonstrate the importance of Aβ in causing familial Alzheimer's disease (reviewed in Hardy, Nature Genet. 1:233-234, 1992). All of these studies suggest that providing a drug to reduce, eliminate or prevent fibrillar Aβ formation, deposition, accumulation and/or persistence in the brains of human patients will serve as an effective therapeutic.
Parkinson's Disease and Synucleinopathies
Parkinson's disease is a neurodegenerative disorder that is pathologically characterized by the presence of intracytoplasmic Lewy bodies (Lewy in Handbuch der Neurologie, M. Lewandowski, ed., Springer, Berlin, pp. 920-933, 1912; Pollanen et al., J. Neuropath. Exp. Neurol. 52:183-191, 1993), the major components of which are filaments consisting of α-synuclein (Spillantini et al., Proc. Natl. Acad. Sci. USA 95:6469-6473, 1998; Arai et al., Neurosci. Lett. 259:83-86, 1999), an 140-amino acid protein (Ueda et al., Proc. Natl. Acad. Sci. USA 90:11282-11286, 1993). Two dominant mutations in α-synuclein causing familial early onset Parkinson's disease have been described suggesting that Lewy bodies contribute mechanistically to the degeneration of neurons in Parkinson's disease and related disorders (Polymeropoulos et al., Science 276:2045-2047, 1997; Kruger et al., Nature Genet. 18:106-108, 1998). Recently, in vitro studies have demonstrated that recombinant α-synuclein can indeed form Lewy body-like fibrils (Conway et al., Nature Med. 4:1318-1320, 1998; Hashimoto et al., Brain Res. 799:301-306, 1998; Nahri et al., J. Biol. Chem. 274:9843-9846, 1999). Most importantly, both Parkinson's disease-linked α-synuclein mutations accelerate this aggregation process, demonstrating that such in vitro studies may have relevance for Parkinson's disease pathogenesis. Alpha-synuclein aggregation and fibril formation fulfills of the criteria of a nucleation-dependent polymerization process (Wood et al., J. Biol. Chem. 274:19509-19512, 1999). In this regard α-synuclein fibril formation resembles that of Alzheimer's β-amyloid protein (Aβ) fibrils. Alpha-synuclein recombinant protein, and non-Aβ component (known as NAC), which is a 35-amino acid peptide fragment of α-synuclein, both have the ability to form fibrils when incubated at 37° C., and are positive with amyloid stains such as Congo red (demonstrating a red/green birefringence when viewed under polarized light) and Thioflavin S (demonstrating positive fluorescence) (Hashimoto et al., Brain Res. 799:301-306, 1998; Ueda et al., Proc. Natl. Acad. Sci. USA 90:11282-11286, 1993).
Synucleins are a family of small, presynaptic neuronal proteins composed of α-, β-, and γ-synucleins, of which only α-synuclein aggregates have been associated with several neurological diseases (Ian et al., Clinical Neurosc. Res. 1:445-455, 2001; Trojanowski and Lee, Neurotoxicology 23:457-460, 2002). The role of synucleins (and in particular, alpha-synuclein) in the etiology of a number of neurodegenerative and/or amyloid diseases has developed from several observations. Pathologically, synuclein was identified as a major component of Lewy bodies, the hallmark inclusions of Parkinson's disease, and a fragment thereof was isolated from amyloid plaques of a different neurological disease, Alzheimer's disease. Biochemically, recombinant α-synuclein was shown to form amyloid-like fibrils that recapitulated the ultrastructural features of alpha-synuclein isolated from patients with dementia with Lewy bodies, Parkinson's disease and multiple system atrophy. Additionally, the identification of mutations within the synuclein gene, albeit in rare cases of familial Parkinson's disease, demonstrated an unequivocal link between synuclein pathology and neurodegenerative diseases. The common involvement of α-synuclein in a spectrum of diseases such as Parkinson's disease, dementia with Lewy bodies, multiple system atrophy and the Lewy body variant of Alzheimer's disease has led to the classification of these diseases under the umbrella term of “synucleinopathies”.
Parkinson's disease α-synuclein fibrils, like the Aβ fibrils of Alzheimer's disease, also consist of a predominantly β-pleated sheet structure. Therefore, compounds found to inhibit Alzheimer's disease Aβ amyloid fibril formation are also anticipated to be effective in the inhibition of α-synuclein/NAC fibril formation, as shown from Examples in the present invention. These compounds would therefore also serve as therapeutics for Parkinson's disease and other synucleinopathies, in addition to having efficacy as a therapeutic for Alzheimer's disease, type 2 diabetes, and other amyloid disorders.
Discovery and identification of new compounds or agents as potential therapeutics to arrest amyloid formation, deposition, accumulation and/or persistence that occurs in Alzheimer's disease, Parkinson's disease, type II diabetes, and other amyloidoses are desperately sought.
Amyloid as a Therapeutic Target for Systemic AA Amyloidosis
Amyloidosis is the generic term for a number of diseases that demonstrate the deposition of insoluble amyloid fibrils in specific organs, which eventually lead to organ dysfunction or failure. These deposits may be limited to one organ, resulting in localized amyloidosis conditions such as Alzheimer's disease (brain) or type 2 diabetes (pancreas), or may be more broadly distributed in the body, resulting in systemic amyloidosis.
Systemic AA amyloidosis involves a particular amyloid protein (referred to as the “AA amyloid” protein) that is deposited in a fibrillar form and is generally associated with chronic inflammatory diseases including rheumatoid arthritis, ankylosing spondylitis, inflammatory bowel diseases, osteomyelitis, chronic infections (e.g. tuberculosis), Hodgkin's disease, leprosy, renal cell carcinoma, and in a familial form known as Familial Mediterranean Fever (Benson and Cohen. Arth. Rheum. 22:36-42, 1979; Kamei et al., Acta Path. Jpn. 32:123-133, 1982; McAdam et al. Lancet 2:572-573, 1975; Metaxas P. Kidney Int. 20:676-685, 1981). Amyloid deposition in these diseases may occur in a variety of different organs including heart, kidney, liver, spleen, gastrointestinal tract, skin and/or lungs (Kisilevsky, R, et al., Nature Med. 1:143-148, 1995). The most common feature of systemic AA amyloidosis is proteinuria, with or without a reduction in the glomerular filtration function of the kidneys. Such amyloid deposition in the kidney may lead to renal failure, whereas amyloid deposition in the heart may lead to heart failure. Thus, the consequences of AA amyloid deposition in systemic organs may be fatal to the patient. Currently, a majority of patients with diagnosed AA amyloidosis generally have a high mortality rate, within 3-7 years from disease onset (Cohen and Connors. J. Path. 151:1-10, 1987; Kisilevsky, R, et al., Nature Med. 1:143-148, 1995). Currently there is no effective treatment, and the discovery of new potential therapeutics for the treatment of AA amyloidosis is desperately needed.
Exact numbers of the cases of systemic AA amyloidosis have not been well documented. However, systemic AA amyloidosis has been reported to occur in approximately 2-5% of rheumatoid arthritic patients in the United States, and in about 5-10% of cases in Europe David et al. Clin. Exp. Rheum. 11:85-90, 1993; Fillpowicz-Sosnowska et al., Arth. Rheum. 21:699-703, 1978; Pras et al. John Hopkins Med. J. 150:22-26, 1982. This disease also occurs in 5-17% of cases of juvenile rheumatoid arthritis in Europe, 1% of cases of Crohn's disease in the United States and Europe, and 15-27% of patients with Familial Mediterranean Fever in the United States and Europe, respectively David et al. Clin. Exp. Rheum. 11:85-90, 1993; Fillpowicz-Sosnowska et al. Arth. Rheum. 21:699-703, 1978; Pras et al. John Hopkins Med. J. 150:22-26, 1982; Saatci et al. Acta Ped. 81:705-706, 1993). It is estimated that there are about 100,000 cases of systemic AA amyloidosis cases in the United States (Hazenberg and Rijswijk. Clinical Rheumatology, 8:661-690, 1994) with a potential market size of approximately $20-$40 million per year in the US alone. In Europe, the number of cases is estimated to be approximately 100,000-400,000.
AA amyloid is common to a host of seemingly unrelated disorders. As described above, clinically AA amyloidosis can be a complication of long-standing inflammation, familial disorders and various forms of malignancy. A common protein being deposited in such different clinical settings suggests that there is a common pathogenetic mechanism operative in all cases (Kisilevsky, R. Can. J. Physiol. Pharmacol. 65:1805-1815, 1987). The AA amyloid protein consists of 76 amino acids with a molecular weight of ˜8,500 (Ein et al. J. Biol. Chem. 247:5653-5655, 1972; Eriksen et al., Proc. Natl. Acad. Sci. U.S.A. 73:964-967, 1976; Sletten et al., Biochem. Biophys. Res. Comm. 69:19-25, 1976). These 76 amino acids correspond to the amino terminal two thirds of a naturally occurring serum protein that is known as SAA or apoSAA (Hoffman et al. J. Exp. Med. 159:641-646, 1984). ApoSAA is an acute phase protein whose serum concentration increases rapidly (within 24 hours) and substantially (500-2000 fold) during any inflammatory response (McAdam and Sipe. J. Exp. Med. 144:1121-1127, 1976; McAdam et al. J. Clin. Invest. 61:390-394, 1978; Sipe J D. Br. J. Exp. Path. 59:305-310, 1978). The amino acid sequence of the AA amyloid protein is identical from patient to patient, regardless of the underlying nature of the inflammatory disturbance that has preceded its deposition. The sequence is also identical to the AA amyloid protein seen in Familial Mediterranean Fever and in patients with Hodgkin's disease or renal cell carcinoma. The AA protein has been found in a number of different species, including humans, ducks, mink, mice and monkeys (Gorevic et al. J. Immunol. 118:1113-1118, 1977; McAdam et al., J. Clin. Invest. 61:390-394, 1978; Sipe et al. Br. J. Exp. Path. 57:582-592, 1976; Sletten et al., Biochem. Biophys. Res. Comm. 69:19-25, 1976; Waalen et al., Eur. J. Biochem. 104:407-412, 1980). Aside from amino acid substitutions that have occurred during evolution, the AA protein is essentially the same to that seen in human (Westermark et al., Comp. Biochem. Physiol. Comp. Biochem. 85:609-614, 1986). In its native state SAA exists as a 160,000 to 200,000 molecular weight complex associated with high-density lipoprotein (Benditt and Eriksen. Proc. Natl. Acad. Sci. U.S.A. 74:4025-4028, 1977; Benditt E P. Proc. Natl. Acad. Sci. U.S.A. 76:4092-4096, 1979; Carlson and Holmquist. Lancet 1:192-197, 1983; Marhaug et al., Clin. Exp. Immunol. 50:382-389, 1982; Skogen et al., Scand. J. Immunolo. 6:1363-1368, 1977; Skogen et al., Scand. J. Immunol. 10:39-45,1979). This association likely occurs within the serum following the secretion of SAA (Hoffman and Benditt. J. Biol. Chem. 257:10510-10517, 1982a; Hoffman and Benditt. J. Biol. Chem. 257:10518-10522, 1982b). SAA can, however, be denatured to release a 12,000 to 14,000 molecular weight subunit, of approximately 103 amino acids, designated SAAL, and all of the immunologic cross-reactivity that exists between SAA and AA proteins is found within the SAAL subunit (Benditt E P. Proc. Natl. Acad. Sci. U.S.A. 76:4092-4096, 1979; Sipe et al., Br. J. Exp. Path. 57:582-592, 1976; Sipe et al., Immunol. Comm. 6:1-12, 1977; Skogen et al., Scand. J. Immunolo. 6:1363-1368, 1977).
Many of these compounds have been found to be useful in the treatment of amyloid diseases such as systemic AA amyloidosis.